Many track-laying vehicles are driven and supported by rubber tracks. [NOTE: As used herein, the term "rubber" relates to any elastic and primarily non-metallic materials such as rubber, elastomers, or combinations thereof used in the manufacture of endless tracks.]
While the invention is applicable to endless tracks for all track-laying vehicles, its particular purpose is to increase the efficiency of such new track-laying all-terrain vehicles of the type specifically designed for normal speed travel over paved highways as well as for appropriate use over unpaved roads and uneven off-road terrain. (E.g., see the track-laying all-terrain vehicle disclosed in U.S. patent application Ser. No. 09/213,650.)
As indicated in the just-identified patent property, there is presently an acute need for a form of vehicle appropriate for both normal highway use and off-road use over snow-covered, very uneven, or muddy terrain. There is significant need for such a vehicle following natural emergencies (snow and wind storms, floods, etc.), and such vehicles are at present particularly needed in developing countries. Unfortunately, almost all available automotive vehicles require infrastructure (paved highways, bridges, etc.) for practical operation, and the developing countries are decades away from having the necessary infrastructure for such conventional vehicles. Further, the only load-carrying off-road vehicles presently in use have either very large wheels or very cumbersome tracks which are heavy, slow moving, and inappropriate for use on paved roads at normal highway speeds. While smaller all-terrain wheeled vehicles are commercially available, these do not carry adequate loads for normal multi-passenger or produce transport, and their drive wheels can easily become mired in heavy mud or snow. Therefore, track-laying vehicles of the type disclosed in the above-identified patent property promise great utility for the future.
Rubber endless tracks are well known and provide supporting contact between a track-laying vehicle and the terrain over which the vehicle is to be moved. The tracks are carried by a plurality of rotating elements (wheels, sprockets, etc.) mounted on the track-laying vehicle, the tracks being maintained in circumferential contact with these rotating elements and being driven thereby (or, in the case of trailer-like non-driven vehicles, being supported for rotation thereon). For purposes of this disclosure, endless tracks are described as having (a) a central plane in the direction of track rotation, (b) an overall track width measured perpendicular to the central plane and parallel to the axes of the vehicle's rotating elements about which the track moves, and (c) an overall track thickness measured vertically parallel to the central plane and perpendicular to the axes of the rotating elements.
Also, most tracks are formed around a basic carcass or belt element having respective interior and exterior surfaces with a predetermined width dimension co-extensive with the track's just-mentioned overall track width. Terrain-contacting lugs are formed integral with the exterior surface of this basic belt element, such lugs having a predetermined lug-thickness dimension.
Known rubber tracks include large lugs having a variety of well-known orientations, e.g., formed generally perpendicular to the track axis, or at an angle to the track axis, or in a chevron or modified-chevron design. Further, one special variety of such tracks, designed to be driven by rubber-tired wheels as disclosed and claimed in the above-identified patent property, has been shown appropriate for the needs of multi-use tracked vehicles that are capable of being driven at highway speeds on paved highways in addition to use over uneven off-road terrain. These latter special tracks include interior lugs for maintaining the track in alignment as it travels over the circumferences of the rubber-tired wheels, such lugs being located either in the center of the interior surface of the track (for designs appropriate for fitting between the tires of dual-wheels) or in two aligned rows near the outside edges of the track (for receiving a single tire therebetween).
Known rubber tracks, when mounted on the rotating wheels of vehicles, exert distinct resistive forces that must be overcome to move the vehicle, i.e., resistive forces in addition to those forces created by the load being carried and/or generated by the terrain. These further resistive forces relate to the additional tensions required to stretch the heavy lugs of the tracks around the wheels over which they are mounted and to the additional friction generated between the tracks and the terrain. While the latter frictional resistive forces are a valuable attribute under wet or snowy conditions, they add undesirably to energy costs when driving the vehicle over flat, hard surfaces.
The rubber endless track designs according to this invention are applicable to all rubber tracks and, particularly, are intended to increase the efficiency of the new off-road/highway-speed tracks specifically designed for multi-use tracked vehicles.